Fix some coverity scan issues

[progier389]

Issue Description
Fix the issue rated as "important" reported by coverity scan static analyzer

Package Version and Platform:

• Platform: Fedora
• Package and version: main branch

Additional context

Using some internal tools to run coverity scan
osh-cli mock-build --config=fedora-rawhide-x86_64 $WS/dist/srpms/389-ds-base-*.src.rpm
But I guess this should also be visible in the github coverity scan test results

Triaged: https://issues.redhat.com/browse/IDMDS-4302

[progier389]

Lasts coverity scan triggered weekly by github action showed that more than 300 of "Use uninitialized variable" have been added. This is due to the #ifndef COVERITY in slapi_pblock_get.